Sheet carrier mechanism for picture telegraphy apparatus

ABSTRACT

A mechanism for the efficient and safe mounting of a sheet being used as a transmitting original or a recording carrier in a picture telegraphy apparatus comprises a cylindrical drum mounted on a continuously rotating driving shaft having a sheet material gripping means on the outer surface of the drum adapted to hold an edge of the sheet material, said gripping means being operated by a single control means associated with the drum and the gripping means whereby a single movement of a control lever on the control means disengages the drum from the drive shaft, stops and locks the drum while disengaging the gripping means from a sheet of material to be held by the drum. After replacement of the sheet a reverse single movement of the control lever engages the sheet material and starts the rotation of the drum.

[45] Mar. 14, 1972 United States Patent Fels et a1.

[54] SHEET CARRIER MECHANISM FOR 2,926,983 3/1960 Fritzinger PICTURE TELEGRAPHY APPARATUS Pr Exa J hWe b 't [72] Inventors: Werner Fels; Klaus Andree, both of Kiel, z g 7 a s z i g & Simpson Germany 73 Assignee: Dr.-lng. Rudolf Hell ABSTRACT [22] Filed: Mar. 19, 1970 A mechanism for the efficient and safe mounting of a sheet being used as a transmitting original or a recording carrier in a [21] Appl. No.:

picture telegraphy apparatus comprises a cylindrical drum mounted on a continuously rotating driving shaft having a sheet material gripping means on the outer surface of the [30] Foreign Application Priority Data Mar. 19, 1969 Germany........................

sociated with the drum and the gripping means whereby a sin- B gle movement of a control lever on the control means disen- Field of Search gages the drum from the drive shaft, stops and locks the drum while disengaging the gripping means from a sheet of material [51] Int.

to be held by the drum. After replacement of the sheet a reverse single movement of the control lever engages the sheet material and starts the rotation of the drum.

2,906,586 Collier...................................346/138 10 Claims,3Drawing Figures Patented March 14, 1972 3 Sheets-Sheet 1 INVENTOR. Werner Fels Klaus Andree HY A'l' l'oluvlsyx Patented March 14, 1972 3,649,004

3 Sheets-Sheet 3 Fig. 3

I N VENTOR.

Werner Fels Klaus Andree BY ATTORNEYS SHEET CARRIER MECHANISM FOR PICTURE TELEGRAPHY APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to picture telegraphy apparatus and more particularly contemplates a mechanism subcombination thereon for facilitating the mounting and unmounting of a sheet being used as a transmitting original or a recording carrier which mechanism includes a rotatably mounted drum having a sheet gripping means thereon and a control means associated therewith whereby the drum may be rapidly and consistently stopped for changing of the sheet.

2. Prior Art According to the prior art, picture telegraphy apparatus for carrying a sheet being used as a transmitting original or a recording carrier are designed in such a way that the means provided on the drum for gripping the sheet of material must be manipulated directly by hand. In addition, the halting of the drum rotation to allow insertion of a new sheet is slow and inconsistent. Thus with the prior art the operator must brake the rotation of the drum so that it stops with the sheet gripping means in an accessible position and then must manipulate the sheet gripping means with at least one hand, change the sheet material, reengage the sheet gripping means with the new sheet by hand and then re-start the rotation of the drum. Not only is this unsafe from the standpoint that the operator must reach into the machinery but also the time required for the sheet changing operation is at the expense of the useful transmitting time of the machine so that the apparatus efficiency is reduced accordingly.

SUMMARY OF THE INVENTION The disadvantages of the prior art are overcome by the apparatus according to the present invention which provides for a safer and quicker operation of the picture telegraphy apparatus by the provision of a sheet carrier mechanism in which the operation and release of the sheet gripping means takes place in conjunction with the actuation of the control means associated with the drum and gripping means for starting and stopping the rotation of the drum. With the apparatus of the present invention the movement of a single switch lever not only serves to stop the rotation of the drum smoothly and at a predetermined position but also locks the drum and disengages the sheet gripping means so that removal and replacement of the sheet may be rapidly effected. Another single movement of the switch lever engages the gripping means, starts the apparatus and locks the switch lever in a disengaged or running position. Moreover, the handle is positioned at a convenient location away from the rotating drum so that the operator can change the sheets only when the drum is locked in an inoperative position. It is a further feature of the present invention that the drive shaft may continue to rotate when the drum has been stopped.

The sheet carrier mechanism of our invention comprises a drum rotatably mounted on a drive shaft set to rotate continuously without stopping. The drum structure is of a hollow cylindrical configuration having an outer cylindrical surface adapted to support a sheet of material and an inner cylindrical surface. End walls may be provided at either end. A sheet material gripping means which is adapted to hold at least an edge of the sheet material is positioned on the drum outer surface and includes an axially aligned groovelike recess in the outer surface of the drum having at least first and second walls with a slot in the first wall and a sheet contacting claw movable through said slot toward and away from the second wall whereby when an edge of the sheet material is placed in the recess the claw may be actuated to clamp the sheet material against the second wall.

A control means is associated with the drum and gripping means and is operable by a single switch means to contemporaneously either engage the gripping means to grip the sheet and unlock and start the rotation of the drum or to disengage the gripping means from the sheet material held on the drum outer surface and to stop and lock the drum against rotation. The control means includes a claw actuator lever mounted on the drum, a switch lever, a switching member, a shaft locking lever, a rotary movement lock and a switching member release means. The switch lever and switching member are mounted in a fixed position relative to the end wall of the drum while the shaft locking lever and the rotary movement lock are mounted on the drum end wall adjacent the claw actuator lever. The switching member is positioned in general axial alignment with the drive shaft and has a first end which is adapted to be moved axially toward and away from the drum end wall and into and out of engagement with the claw actuator lever, the shaft locking lever, and the rotary movement lock. Movement of the switching member is effected by the rotation of the switch lever which compresses a resilient compressible member on the switching member and at the same time activates the switching member release means which allows the resilient member to push the switching member into the plane of the claw actuator lever, shaft locking lever and rotary movement lock whereby the drum is disengaged from the drive shaft, stopped and locked against rotation and the gripping means is disengaged. The switching member release groovelike is operated by a camming surface on the interior of the drum so that the drum is stopped quickly and consistently in the same position relative to the switching member.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

FIG. 1 is a cross-sectional view taken in a plane perpendicular to the drum axis showing the drum and the sheet material receiving recess and the claw;

FIG. 2 illustrates the drum end surface on which the claw actuating lever, drive shaft locking lever and locking lever are mounted; and,

FIG. 3 is a perspective view of the control means adjacent the drum end wall with the levers omitted so that the parts may be more easily seen.

DESCRIPTION OF THE PREFERRED EMBODIMENT The sheet carrier mechanism of the present invention which is particularly adaptable to picture telegraphy may be seen from the cross-sectional view of FIG. I to include a drum generally indicated at 10, having a hollow cylindrical wall 12 with an inner surface and an outer surface 12b. The drum 10 is mounted for rotation on a drive shaft 15. The cylindrical wall 12 of the drum has an axially aligned groove-like recess 21 therein of a length to accommodate the width of the sheet material to be held therein. Thus, the recess may extend entirely across the drum or only across a portion of the drum length. As shown the recess 21 has at least a first wall surface 21a and a second wall surface 21b which surfaces may converge towards each other. A slot 24 in the first wall 210 allows a retaining claw 20 to pass therethrough from the interior of the drum 10. The claw 20 may take the form of a hooklike member having a first end 20a attached to a pivotal member 26 which pivotal member is mounted between the end walls of the drum 10. A second clamping end 20b of the claw 20 is pivotally movable toward and away from the second wall 21b of the recess 21 whereby it may be actuated to clamp the edge of a piece of sheet material against the second wall 21b. A depending arm member 34 attached to the pivot member 26 has attached thereto a resilient biasing means 30 which biases the claw 20 toward the wall 21b of the recess 21. The resilient means 30 may take the form of a tension spring having one end attached to the arm 34 and the other end attached to a projection 14 on the inner surface 12a of the drum 10. The arm of the lever 34 has a portion extending parallel to the axis 15 of the drum and as may be seen in FIG. 2 projects through an arcuate slot 38 in a front end wall 32 of the drum 10.

Referring to FIG. 2 the engagement of the claw pivot arm 34 with a slot 35 in the claw actuator lever 37 may be seen. The lever 37 includes a cutout portion 370 into which the slot 35 opens so that as the claw actuator lever 37 pivots about a pivotal point 36 affixed to the end wall 32 the actuator arm 34 may be moved through the end wall slot 38 by engagement of the slot 35 against the outside of the arm 34. The resilient spring means 30 as shown in FIG. 1 will serve to bias the actuator lever 37 clockwise about the pivot point 36.

Movement of the claw actuator lever 37 in a counterclockwise direction about the pivot point 36 and against the bias of spring 30 is caused by the engagement of an outer edge 37b of the actuator lever 37 with a switching roller shown in dotted lines at 59. As will be described with respect to FIG. 3 the switching roller 59 which is attached to a switching member 56 is moved into the plane of the claw actuator lever 37 when it is desired to stop the rotary movement of the drum and release the claw 20 of the gripping means so that the sheet material on the drum may be changed. Thus, after the switching roller 59 is in the plane of the actuator lever 37 further rotary movement of the drum 10 in the clockwise direction indicated by the arrow 18 will move the edge 3712 into contact with the roller 59 thereby moving the actuator lever 37 from its rest position against the force of the spring 30 in a counterclockwise direction which in turn moves the arm 34 in the slot 38 and pivots the claw 20 away from the recess wall 21b.

In addition to the claw actuator lever 37 there is provided a shaft locking lever 40 also pivotally mounted on the pivot point 36 and having a catch portion 42 on first end 40a. The portion 42 is biased by a spring means 43 against the outer surface a of the drive shaft 15 so that the portion 42 will engage a suitable locking notch 17 in a drive shaft 15. The spring means 43 may be of a suitable tension coil spring having one end 43a attached to the locking lever 40 biasing it in a clockwise direction about the pivot point 36 and a second end 43b attached to a suitable means 31 on the end wall 32. The lever 40 includes at a second end 40b a generally radially outwardly extending stop member 45 which as the drum 10 is turning in a direction 18 will engage the switcher roller 59 thereby pivoting the lever 40 in a counterclockwise direction about pivot point 36 and disengaging the end portion 42 from the notch 17 in the drive shaft 15 thereby stopping the rotary movement of the drum 10 while allowing the drive shaft 15 to continue to rotate. This operation has the advantage that the drum may be quickly stopped and started. In addition the abutment of the stop portion 45 against the switching roller 59 provides a positive stop that will leave the sheet material receiving recess in a constant position every time the drum is stopped. Of course, this position may be adjusted so that the drum always stops with the gripper means readily exposed in the best possible position for changing the sheet material.

To assure the gradual and smooth stopping of the drum 10 and to lock the stopped drum against counterclockwise movement we have provided a rotary movement locking lever 41 which is pivotally attached to the end wall 32 at the pivot point 46. A resilient spring means 48 biases the camming edge 41a of the locking lever 41 counterclockwise towards the inner surface 121: of the drum 10 so that when the lever 41 is adjusted as shown to engage the switching roller 59 shortly after the switching roller 59 engages the claw actuator lever camming edge 37b the switching roller 59 must push the rotary movement locking lever 41 out of its way and in a clockwise direction against the bias With a further movement of the drum in a clockwise direction, the lever 40 is then swiveled in a counterclockwise direction, and the projection 42 decouples from the notch 17 and the shaft 15, i.e., drum and shaft are decoupled. While the cam plate 37 is moving along the roller 59, the lever 41 is also moved and functions to hold the roller 59 after the decoupling of the nose 42 from the notch 17 by moving outwardly again to clamp the roller 59 when its curved part 41a has slid past the roller 59. After this process, the shaft 15 rotates continuously without thereby taking along the drum 10. It will be understood by those skilled in the art that the relative positions of the camming edges 37!) and 41a as well as the tension force on these members may be adjusted as suits the particular operating conditions. When the switching roller 59 abuts the stop 45 it moves the lever 40 counterclockwise toward the shaft 15 and the rotary movement lock member 41 will pivot so that edge 410 will pass over roller 59 and snap toward the rim with its edge 41b in engagement with the opposite side of the roller 59 as the stop member 45 prevents a turning back of the drum when the switching roller 59 has engaged the stop member 45. This locks the drum in a stop position between stop 45 and edge 41b and allows the quick and convenient changing of the sheet material. From the above description it may be now understood that when the switching roller 59 is thrust into the plane of the levers 37, 40 and 41, the claw 20 is disengaged from the sheet material while the drum 10 itself is disengaged from the drive shaft 15, stopped and locked in place with the switching roller 59 being clamped between the stop member 45 and the edge 411). Of course, when the switching roller 59 is removed from between the lever portions 45, 41b of the levers 40, 41 the spring means 30 pivots the claw 20 to grip any sheet material in the recess 21 and the spring 43 forces the end portion 42 of the lever 40 against the drive shaft 15 so that it enters the notch 17 thereby causing the drum to rotate with the shaft 15.

The stopping functions of uncoupling, stopping and locking the drum 10 and disengaging the retaining claw 20 as well as the reverse starting functions are effected by the actuation of a single switch on a fixed part of the apparatus. This control function may be seen more clearly with reference to the perspective view of FIG. 3 which shows a mounting means generally indicated at 55 positioned in front of the drum end wall 32. The apparatus to which the mounting means 55 is attached has not been shown for purposes of clarity of presentation. It will be understood, however, that it is fixed to the apparatus at a convenient location away from the rotating drum depending on the convenience of the operator. As shown the mounting means 55 may take the form of a U-shaped element. A switching member 56 in the form of a shaft is mounted in holes 51, 52 on spaced portions of the support means 55 so that it may be axially displaceable in a direction as indicated by the arrow 53. The switching roller 59 is attached to a first end 56a of the switching member 56 and a second end 56b which projects beyond the support 55 has a notch 56 therein. As shown the switching member 56 is in an inoperative first position out of the plane of levers 37, 40 and 41. These levers have been omitted in FIG. 3 so that the other parts of the mechanism may be more easily seen and understood. A catch member 57 extending transverse to the switching member 56 in the area of the retracted position of the notch 56c is pivotally attached to the support 55 at a first end 57a and is biased by a suitable means 58 against the switching member 56 so that it will engage the notch 56c when it is in its inoperative retracted position. This locks the switching member 56 and the roller 59 out of the plane of the levers 37, 40 and 41. The resilient biasing means 58 may take the form of a metal spring extending between a second end 57b and a projection 55a on the support 55.

Movement of the switching member 56 to the position as shown where it is locked in its retracted position is caused by movement of a switch lever 61 to the start position. The switch lever 61 is attached to a shaft 65 which in turn has a first arm 63 and a second arm 64 attached thereto in spaced relation therealong. A cam member 66 on the outer end of the second arm 64 bears against a first flange 69 as the shaft 65 is rotated by the switch lever 61. When the switch lever 61 has reached the start position the switching member 56 will have been moved axially so that the roller 59 is disengaged from the levers 37, 40 and 41 and the notch 560 is below the catch member 57 so that it is biased therein by the resilient means 58. In this position the drum will be rotating. The switch lever at this point may be moved to the middle or running position indicated at m.

When it is desired to stop the rotation of the drum the switch lever 61 is rotated counterclockwise as indicated by the arrow 62 from the start or middle running position to the stop position indicated. The shaft 65 is suitably supported for rotation by the support member 55 and the apparatus, not shown. During this movement the cam member 66 on the outer end of the second arm 64 moves into engagement with a collar 71 that is slidably mounted on the rodlike switch member 56. The collar 71 abuts one end of a coil spring member 72 that is advantageously coiled about the switching member 56. A second flange 76 fixed to the switching member 56 allows the spring 72 to be compressed by the movement of the cam 66 against the slidable collar 71. As the compression takes place the catch member 57 remains in the notch 56c and prevents axial movement of the switching member 56. Simultaneously with the compression of the spring 72 the free end of the lever 63 which carries a small wedge 77 thereon engages a central portion 80a of a release actuator rod 80 that is supported adjacent its opposite first end 80b and second end 800 in elongated slots 55b and 550 in the spaced flanges of the support member 55. As the wedge member 77 engages the rod 80 it tends to lift it upwardly, however, the second end 800 is held down by the force of the resilient means 58 acting on the catch member 57 which bears against the second end 800. As a result the unrestrained first end 80b of the rod is moved upwardly and toward the inner surface 12a of the drum 10. The release actuator rod 80 may have a roller 82 rotatably mounted on its first end which roller extends interior of the drum 10. As the first arm 63 continues to raise the rod 80 the roller 82 approaches the inner surface of the drum and engages a camming projection 84 which is positioned on the inner surface in fixed relation to the levers 37, 40 and 41. The camming surface 84 will drive the roller 82 downwardly as indicated by the arrow 85 thereby pivoting the rod 80 about the wedge 77 on the first arm member 63 and lifting the second end 80c upwardly to disengage the catch member 57 from the notch 56c. Upon this disengagement the resilient force stored in the spring 72 snaps the switching member 56 and its attached switching roller 59 toward the drum end wall 32 and in a position as indicated for example by the dotted lines 59 in FIG. 2. The movement of the switching roller 59 into the plane of the levers 37, 40 and 41 thus is timed to take place prior to the engagement of the levers with the switching roller. The drum 10 will thus be disengaged from the drive shaft 15, stopped, locked against rotary movement and the claws of the gripping means disengaged from the sheet material as explained in detail with respect to FIG. 2.

To restart the drum rotation the switch lever 61 is moved to the start position so that the wedge 77 allows the release actuator rod 80 to move away from the drum. inner surface under the force of gravity or other means and the cam 66 bears against the fixed collar 69 to move the switching member 56 axially out of the plane of the levers 37, and 41 until the catch 57 reengages the notch 56 to hold the switching roller 59 in a retracted inoperative position.

Having thus described the many useful and novel features of the sheet carrier mechanism of the presentinvention it will be apparent that the many disadvantages of the prior art have been clearly overcome by a simple, efficient and safe means that will allow very rapid changing of the sheet material so that the efficiency of the apparatus is improved accordingly. Although only a specific embodiment of the invention has been illustrated and described herein, we realize that certain changes and modifications therein may well occur to those skilled in the art within the broad teachings of our invention and therefore it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications and equivalents as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention:

1. A sheet carrier mechanism comprising a drum rotatably mounted on a drive shaft, said drum having an outer surface adapted to support a sheet of material, a sheet material gripping means on said drum outer surface adapted to hold at least an edge of said sheet material, a control means associated with said drum and gripping means operable by a single switch means to contemporaneously either engage the gripping means to grip the sheet and start the rotation of said drum or to stop the rotation of the drum and disengage said gripping means from said sheet of material adapted to be held on said drum outer surface.

2. A sheet carrier mechanism according to claim 1 wherein said gripping means includes an axially aligned groovelike recess in the outer surface of said drum, said recess having at least first and second walls, a slot in said first wall. a claw movable through said slot and toward and away from said second wall whereby said claw may be actuated to clamp against said second wall at least an edge of said sheet material placed in said recess.

3. A sheet carrier mechanism according to claim 2 wherein said control means includes a claw actuator lever mounted on said drum and a switch lever and a switching member not mounted on said drum but in fixed relation adjacent thereto, said switch lever being operable to move said switching member into and out of engagement with said claw actuator lever and thereby move said claw away from said second wall.

4. A sheet carrier mechanism according to claim I, wherein said drive shaft is set to rotate continuously without stopping, and wherein said control means includes a shaft locking lever operable to lock said drum to said shaft for rotation of said drum therewith and to unlock said drum from said shaft to allow stopping of said shaft for insertion of the sheet material, said shaft locking lever being actuated contemporaneously with said gripping means by said switching means.

5. A sheet carrier mechanism according to claim 3 wherein a switching member release means is associated with said switching member to lock the switching member in a position which allows the drum to be rotatably driven by the drive shaft.

6. A sheet carrier mechanism according to claim 1 wherein said control means includes a switching member positioned in general axial alignment with said drive shaft and has a first end which is adapted to be moved from a first position stopping the rotation of said drum to a second position wherein said drum may start and rotate, said switching member being moved between said first and second positions by said switch means, said switch means having first and second arms thereon, said second arm engaging a collar fixed on said switching member to move said switching member from said first position to said second position, said second arm engag ing a sliding collar on said switching member for compressing a resilient spring on said switching member prior to the release of said switching member by a release means, said switching member being adapted to snap from said second to said first positions upon release by said release means, said release means comprising a rod having a first end adapted to project within said cylindrical wall and a second end adapted to engage a catch member biased against said switching member and, said catch member engaging a notch in said switching member to hold said switching member in said second position, said drum having a cam surface on its inner surface, said first arm of said switch means being adapted to engage said release rod and move said firstend into engagement with said camming surface of said drum thereby allowing the rod to pivot about said first arm and move said catch out of said notch on said switching member to thereby release said switching member for movement from said second to said first position.

7. A sheet carrier mechanism according to claim 3 wherein said control means further includes a rotary movement lock adapted to engage said switching roller to thereby lock said drum against reverse movement.

8. A sheet carrier mechanism according to claim 1 wherein said control means includes first and second lever means mounted for rotation with said drum means, each of said lever means being rotatably mounted about a pivot point, each of said levers being spring biased against rotation about said pivot point, said first lever means being operable upon rotation about its pivot point to operate said gripping means, said second lever means being operable upon rotation about its pivot point to disengage said drum from said drive shaft, a switching roller means movable by said switch means into and out of engagement with said first and second lever means to contemporaneously either engage the gripping means to grip the sheet and start the rotation of said drum or to stop the rotation of said drum and disengage said gripping means from said sheet material.

9. A sheet carrier mechanism according to claim 8 wherein said control means includes a third lever means mounted for rotation with said drum means, said third lever means being rotatably mounted about a pivot point and spring biased against rotation about said pivot point, said third lever means being operable upon reciprocal movement about its pivot point to engage said switching roller means and cooperate with said second lever means to lock said drum against rotation in a predetermined position.

10. A sheet carrier mechanism according to claim 1 wherein said switch means moves roller means into engagement with camming means rotating with said drum means whereby the forces necessary to contemporaneously either engage the gripping means to grip the sheet and start the rotation of said drum, or to stop the rotation of the drum and disengage said gripping means are provided by said drum and said camming means. 

1. A sheet carrier mechanism comprising a drum rotatably mounted on a drive shaft, said drum having an outer surface adapted to support a sheet of material, a sheet material gripping means on said drum outer surface adapted to hold at least an edge of said sheet material, a control means associated with said drum and gripping means operable by a single switch means to contemporaneously either engage the gripping means to grip the sheet and start the rotation of said drum or to stop the rotation of the drum and disengage said gripping means from said sheet of material adapted to be held on said drum outer surface.
 2. A sheet carrier mechanism according to claim 1 wherein said gripping means includes an axially aligned groovelike recess in the outer surface of said drum, said recess having at least first and second walls, a slot in said first wall, a claw movable through said slot and toward and away from said second wall whereby said claw may be actuated to clamp against said second wall at least an edge of said sheet material placed in said recess.
 3. A sheet carrier mechanism according to claim 2 wherein said control means includes a claw actuator lever mounted on said drum and a switch lever and a switching member not mounted on said drum but in fixed relation adjacent thereto, said switch lever beinG operable to move said switching member into and out of engagement with said claw actuator lever and thereby move said claw away from said second wall.
 4. A sheet carrier mechanism according to claim 1, wherein said drive shaft is set to rotate continuously without stopping, and wherein said control means includes a shaft locking lever operable to lock said drum to said shaft for rotation of said drum therewith and to unlock said drum from said shaft to allow stopping of said shaft for insertion of the sheet material, said shaft locking lever being actuated contemporaneously with said gripping means by said switching means.
 5. A sheet carrier mechanism according to claim 3 wherein a switching member release means is associated with said switching member to lock the switching member in a position which allows the drum to be rotatably driven by the drive shaft.
 6. A sheet carrier mechanism according to claim 1 wherein said control means includes a switching member positioned in general axial alignment with said drive shaft and has a first end which is adapted to be moved from a first position stopping the rotation of said drum to a second position wherein said drum may start and rotate, said switching member being moved between said first and second positions by said switch means, said switch means having first and second arms thereon, said second arm engaging a collar fixed on said switching member to move said switching member from said first position to said second position, said second arm engaging a sliding collar on said switching member for compressing a resilient spring on said switching member prior to the release of said switching member by a release means, said switching member being adapted to snap from said second to said first positions upon release by said release means, said release means comprising a rod having a first end adapted to project within said cylindrical wall and a second end adapted to engage a catch member biased against said switching member and, said catch member engaging a notch in said switching member to hold said switching member in said second position, said drum having a cam surface on its inner surface, said first arm of said switch means being adapted to engage said release rod and move said first end into engagement with said camming surface of said drum thereby allowing the rod to pivot about said first arm and move said catch out of said notch on said switching member to thereby release said switching member for movement from said second to said first position.
 7. A sheet carrier mechanism according to claim 3 wherein said control means further includes a rotary movement lock adapted to engage said switching roller to thereby lock said drum against reverse movement.
 8. A sheet carrier mechanism according to claim 1 wherein said control means includes first and second lever means mounted for rotation with said drum means, each of said lever means being rotatably mounted about a pivot point, each of said levers being spring biased against rotation about said pivot point, said first lever means being operable upon rotation about its pivot point to operate said gripping means, said second lever means being operable upon rotation about its pivot point to disengage said drum from said drive shaft, a switching roller means movable by said switch means into and out of engagement with said first and second lever means to contemporaneously either engage the gripping means to grip the sheet and start the rotation of said drum or to stop the rotation of said drum and disengage said gripping means from said sheet material.
 9. A sheet carrier mechanism according to claim 8 wherein said control means includes a third lever means mounted for rotation with said drum means, said third lever means being rotatably mounted about a pivot point and spring biased against rotation about said pivot point, said third lever means being operable upon reciprocal movement about its pivot point to engage said switching roller means and cooperate wIth said second lever means to lock said drum against rotation in a predetermined position.
 10. A sheet carrier mechanism according to claim 1 wherein said switch means moves roller means into engagement with camming means rotating with said drum means whereby the forces necessary to contemporaneously either engage the gripping means to grip the sheet and start the rotation of said drum, or to stop the rotation of the drum and disengage said gripping means are provided by said drum and said camming means. 